1. Field of the Invention
The present invention relates to a display device equipped with a light-emitting element and a method for manufacturing the same.
2. Description of the Related Art
In recent years, a large-sized screen and high-definition are promoted in a display device having a light-emitting element and a liquid crystal element, which the number of wirings such as a signal line and a scanning line, and the length of a wiring tend to increase. Therefore, it is necessary to prevent voltage drop due to wiring resistance, a signal writing defect, a gradation defect, and the like.
Thus, there is a configuration in which an auxiliary wiring made of a transparent conductive film is connected to the transparent electrode that the light-emitting element has, interposing an anisotropical conductor (refer to Patent Document 1). According to Patent Document 1, effective resistance of the transparent electrode can be lowered. Furthermore, it is possible to apply constant voltage to the light-emitting element; therefore, it is mentioned that a display defect such as display unevenness can be prevented. [Patent Document 1] Japanese Patent Laid-Open No. 2002-33198
According to a method different from Patent Document 1, an object of the invention is to provide a display device that can reduce effective resistance of an electrode such as a transparent electrode and a wiring, and furthermore which can apply constant voltage to a light-emitting element.
The display device includes a light-emitting element having a first electrode and a second electrode to apply voltage to a light-emitting layer. The second electrode can be shared in light-emitting elements, that is the second electrode can be formed without patterning over the light-emitting layer in pixels. It is necessary for such second electrode to apply same voltage to the light-emitting elements.
In addition, when light from the light-emitting layer is emitted to an opposite side of a substrate in which a semiconductor element typified by a TFT is provided (hereinafter, referred to as a top emission), the second electrode needs to be transparent. Therefore, the second electrode has a configuration having a transparent conductive film, for example, an ITO (indium tin oxide). However, the resistance of the transparent conductive film is high. Furthermore, the second electrode may use a thin film of a metal film; however, the resistance has become high due to the thin film-thickness. As a result, it is concerned that low power consumption of the display device is disturbed.
Especially, as a display device gets larger in size, it becomes more important to apply constant voltage to the light-emitting layer. However, as mentioned above, resistance of the second electrode is high; and consequently it is concerned that power consumption of a display device is increased.